title: Oxytetracycline treatment reduces bacterial diversity of intestinal microbiota of Atlantic salmon.
abstract: The effect of oxytetracycline (OTC) treatment on intestinal bacterial populations in juvenile Atlantic salmon Salmo salar was evaluated. Oxytetracycline was administered by way of medicated feed to fish held in experimental tanks. Restriction fragment length polymorphism and sequencing of 16S rDNA from isolates were used to analyze the intestinal microbiota before, during, and after OTC administration. The microbiota from untreated fish was more diverse, consisting mainly of Pseudomonas, Acinetobacter, Bacillus, Flavobacterium, Psycrobacter, and Brevundimonas spp. In contrast, the microbiota of the OTC-treated group was characterized by lower diversity and consisted only of Aeromonas, clustering with A. sobria and A. salmonicida. Antibiotic-resistant isolates were identified as Aeromonas spp.; sequencing the resistance determinant showed it to be the tetE gene. Overall, OTC treatment changed the composition of the intestinal microbiota of Atlantic salmon, as evidenced by a reduction in bacterial diversity. These results support the current concern that antibiotic treatment can facilitate the proliferation of opportunistic bacteria by eradicating competing microorganisms.
authors.affiliation: Laboratorio de Biotecnología, Instituto de Nutrición y Tecnología de los Alimentos, Universidad de Chile, El Líbano 5524, Macul, 6903625 Santiago, Chile.
authors.forename: Paola
authors.initials: P
authors.lastname: Navarrete
authors.forename: Pamela
authors.initials: P
authors.lastname: Mardones
authors.forename: Rafael
authors.initials: R
authors.lastname: Opazo
authors.forename: Romilio
authors.initials: R
authors.lastname: Espejo
authors.forename: Jaime
authors.initials: J
authors.lastname: Romero
mesh_terms: D000333:Aeromonas / Q000187:drug effects / Q000254:growth & development; D000821:Animal Feed; D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001419:Bacteria / Q000187:drug effects / Q000254:growth & development; D044822:Biodiversity; D015169:Colony Count, Microbial; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D004275:DNA, Ribosomal / Q000737:chemistry / Q000235:genetics; D024881:Drug Resistance, Bacterial; D005393:Fish Diseases / Q000517:prevention & control*; D041981:Gastrointestinal Tract / Q000382:microbiology*; D008826:Microbial Sensitivity Tests; D010118:Oxytetracycline / Q000494:pharmacology*; D012150:Polymorphism, Restriction Fragment Length; D012336:RNA, Ribosomal, 16S; D020317:Salmo salar / Q000382:microbiology*
chemical_list: D000900:Anti-Bacterial Agents; D004269:DNA, Bacterial; D004275:DNA, Ribosomal; D012336:RNA, Ribosomal, 16S; D010118:Oxytetracycline